Analytical Solutions for Deep-Buried Lined Tunnels Considering Longitudinal Discontinuous Excavation in Rheological Rock Mass

Abstract

For tunneling in a deep, soft rock mass, rock deformation and lining pressure, which are time-dependent behaviors, are mainly affected by rock rheology and longitudinal excavation processes. In practice, tunneling operations are often suspended due to various reasons, which will result in changes to the time-dependent behaviors of tunnel systems. To investigate the discontinuous advancement of the tunnel face in a soft rheological rock mass, in this study, closed-form analytical solutions are presented to analyze the time dependency of deep-buried circular lined tunnels. In the derivation, four types of viscoelastic models are utilized to consider the different creep behaviors of the host rock. The coupling effect between rock rheology and tunnel face advancement is also taken into account. To realistically simulate the process of tunnel face advancement, five different excavation methods are considered in the solutions that depend on whether the face stops and on the changes of advancing speeds before and after stoppage. The proposed solutions are validated by comparing the calculated results with those predicted by a finite difference simulation. According to the provided solutions, a series of parametric analyses are systematically performed to investigate the influences of the lining installation time, the duration of the tunnel face stoppage, the tunnel face advancing parameters, and the rheological parameters of the rock on rock stresses and displacement, as well as the support pressure. Finally, the proposed solutions are successfully applied to the Rong Jiawan tunnel when an excavation stoppage occurs halfway before tunnel completion, and the theoretical predictions are in good agreement with the field monitoring data. The solutions proposed in this paper provide an efficient analytical approach for predicting and analyzing the discontinuous excavation of rheological tunnels.